If your drop down list is based off a complex type, meaning the data type is something other than text and you have to select a property for the display field then this is easy. Your drop down list has a property called Post Form on Value Change. Make sure it's checked. Add a merge label to your form and in the variable picker you will see a special item called ThisFormData. Drill into this and you should see your variable name for the selected item of your drop down. You can choose whatever properties you wish to display. That should do it. If you want to make the user experience better put the drop down and merge label in a component called DynamicUpdatePanelComponent and that portion of the page will be refreshed via AJAX without the whole page refreshing.

You Can try creating a sub category for the it . and what rhammer mentioned is correct. but it would be more precise if you can provide the detailed outcome that you would like to achieve.

Thanks rhamner, that got me going down the right path and now everything is working perfectly